// 2025/10/29
// 交错字符串

class Solution {
public:
    bool isInterleave(string s1, string s2, string s3) {
        if(s1.size() + s2.size() != s3.size())
            return false;
        int m = s1.size(), n = s2.size();
        vector<vector<bool>> dp(m + 1, vector<bool>(n + 1));
        dp[0][0] = true;
        for(int i = 1; i <= m; i++)
        {
            if(s1[i - 1] == s3[i - 1])
                dp[i][0] = dp[i - 1][0];
        }
        for(int j = 1; j <= n; j++)
        {
            if(s2[j - 1] == s3[j - 1])
                dp[0][j] = dp[0][j - 1];
        }
        for(int i = 1; i <= m; i++)
        {
            for(int j = 1; j <= n; j++)
            {
                if(s1[i - 1] == s3[i + j - 1])
                {
                    dp[i][j] = dp[i][j] | dp[i - 1][j];
                }
                if(s2[j - 1] == s3[i + j - 1])
                {
                    dp[i][j] = dp[i][j] | dp[i][j - 1];
                }
            }
        }
        return dp[m][n];
    }
};